The current analog front-end integrated circuits include complex parts for signal preconditioning, such as mixers or baseband amplifiers (BBAs), which either amplify or attenuate the received signal before digitizing it with the two separate ADCs.
As illustrated in FIG. 1, the integrated circuit 100 includes an antenna 101, a High Frequency Attenuator (“HF-ATT”) 102, two mixers 103 and 104, two low pass filters 105, 106, two BBAs 107, 108, two ADCs 109, 110, and a DSP 111.
As two signal paths are available, every function needs to be implemented twice, which adds redundancy to the system. The reason for having two signal paths is that the transmitted information can either be situated in the amplitude or phase of the carrier signal or in both of them.
Therefore I/Q demodulation is required for reconstruction of the transmitted signal in order to obtain the necessary data.
The two ADCs 109 and 110 are required which cost more chip space and power consumption and because the integrated circuit 100 needs to produce two clocks and where one clock is 90° phase shifted from the other, there is a lag time in the phase shifted channel which adds additional noise to the signal which contributes to a lower SNR.
Further, the mixers 103 and 104 in FIG. 1 can exhibit poor power supply rejection which adds additional noise to the signal and the mixers 103 and 104 can perform phase noise to amplitude noise conversion due to the uncertainty of the clock signal.